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1.
C. Brügger F. Kämpfer M. Pepe U.-J. Wiese 《The European Physical Journal B - Condensed Matter and Complex Systems》2006,53(4):433-437
The long-range forces between holes in an antiferromagnet are due to
magnon exchange. The one-magnon exchange potential between two holes is
proportional to cos(2 ϕ)/r
2 where r is the distance
vector of the holes and ϕ is the angle between r and an axis of
the square crystal lattice. One-magnon exchange leads to bound states of holes
with antiparallel spins resembling d-wave symmetry. 相似文献
2.
The behavior of the thermal conductivity k(T) of bulk faceted fullerite C60 crystals is investigated at temperatures T=8–220 K. The samples are prepared by the gas-transport method from pure C60, containing less than 0.01% impurities. It is found that as the temperature decreases, the thermal conductivity of the crystal
increases, reaches a maximum at T=15–20 K, and drops by a factor of ∼2, proportional to the change in the specific heat, on cooling to 8 K. The effective phonon
mean free path λ
p, estimated from the thermal conductivity and known from the published values of the specific heat of fullerite, is comparable
to the lattice constant of the crystal λ
p∼d=1.4 nm at temperatures T>200 K and reaches values λp∼50d at T<15 K, i.e., the maximum phonon ranges are limited by scattering on defects in the volume of the sample in the simple cubic
phase. In the range T=25−75 K the observed temperature dependence k(T) can be described by the expression k(T)∼exp(Θ/bT), characteristic for the behavior of the thermal conductivity of perfect nonconducting crystals at temperatures below the
Debye temperature Θ (Θ=80 K in fullerite), where umklapp phonon-phonon scattering processes predominate in the volume of the
sample.
Pis’ma Zh. éksp. Teor. Fiz. 65, No. 8, 651–656 (25 April 1997) 相似文献
3.
Anomalous behavior of the interlayer resistance of a BSCCO-2212 crystal in a parallel magnetic field
V. N. Zavaritskii 《JETP Letters》1996,63(2):139-145
The electrical resistance across the Cu-O layers of a BSCCO-2212 single crystal is investigated in the range of angles 0°⩽φ⩽90°
between the magnetic field H⩽15 T and the ab plane. It is found that the temperature dependence R(T) at the transition into the mixed state is much sharper for φ≃0° than for 1°≲φ≲90°, where R is determined by the perpendicular component of the magnetic field and is described by the Arrhenius law R∼exp(−U/T). For H∥ ab hysteretic jumps in R(T, H), which vanish as the current increases, are observed at fields in the range 5.5⩽H⩽11 T. This effect can be attributed to
a commensurate phase transition in a lattice of Josephson vortices.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 2, 123–128 (25 January 1996) 相似文献
4.
K. N. Mikhalev S. V. Verkhovskii A. P. Gerashchenko Yu. V. Piskunov A. Yu. Yakubovskii A. P. Rusakov 《JETP Letters》1999,70(5):346-351
The spin-lattice relaxation times T
1 in Ba1−x
KxBiO3 (x=0.3, 0.4, 0.5) were measured in the normal temperature range (20–300 K).A substantial contribution to the spin-lattice relaxation
rate from dynamic local distortions of the crystal lattice near potassium atoms is found. The activation energy of this process
increases with decreasing potassium concentration, and the frequency of lattice excitations decreases. The nature of the low-frequency
lattice dynamics is discussed.
Pis’ma Zh. éksp. Teor. Fiz. 70, No. 5, 344–349 (10 September 1999) 相似文献
5.
The excess 1/f noise in a random lattice with bond resistances r∼exp(−λx), where x is a random variable and λ≪1, is studied theoretically. It is shown that if the correlation function {δr
2}∼r
r
θ+2, then the relative spectral density of the noise in the system is expressed as C
e∼λm exp(−λ(1−p
c)), where p
c is the percolation threshold and m=νd (ν is the critical exponent of the correlation length and d is the dimensionality of the problem). It is hypothesized that the exponent m possesses a dual universality: It is independent of 1) the geometry of the lattice and 2) the θ-mechanism responsible for
the generation of the local noise. Numerical modeling in a three-dimensional lattice gives m=52.3 for θ=1 and θ=0, in agreement with the hypothesis.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 8, 614–618 (25 April 1996) 相似文献
6.
The temperature dependence of the Young’s modulus E of paramagnetic lutetium has been studied. It has been shown that an important reason for the dependence E(T) is thermal expansion of the crystal lattice, which also leads to a change in the Debye temperature Θ. The effect of this
factor is also revealed in the thermodynamic properties of metals. In particular, we have shown that there is another contribution
to variation of the total specific heat of lutetium, associated with the Θ(T) dependence and comparable with the electronic contribution.
Fiz. Tverd. Tela (St. Petersburg) 40, 1581–1584 (September 1998) 相似文献
7.
The shape of the EPR line in a thin (=λ/2, where λ is the London penetration depth of the magnetic field in the superconductor) paramagnetic film deposited on the surface of
an anisotropic superconductor is calculated in an oblique magnetic field with allowance for the inhomogeneity of the local
magnetic field of the Abrikosov vortex lattice. It is shown that, as the tilt angle of the external magnetic field is varied,
the shape of the EPR line changes noticeably. This fact can give additional information about the superconductor parameters
(the symmetry type of the vortex lattice and the anisotropy parameter of the superconductor).
Fiz. Tverd. Tela (St. Petersburg) 41, 386–388 (March 1999) 相似文献
8.
V. A. Popov 《Physics of the Solid State》1998,40(7):1079-1080
The Korringa-Kohn-Rostoker method with Green’s function averaged over the atomic configurations in a complex Ising lattice
and a muffin-tin potential was used to calculate the electronic-band structure in lithium containing vacancies and s, p, and d impurities. It is shown that substantial changes in the profile of the Fermi surface do not lead to necking, as was postulated
previously, but cause splitting of the electronic states at the face of the Brillouin zone. This is attributed to the reduced
symmetry of the crystal lattice with impurity excitation of the electronic-subsystem.
Fiz. Tverd. Tela (St. Petersburg) 40, 1185–1186 (July 1998) 相似文献
9.
V. G. Vaks 《JETP Letters》1998,67(6):422-428
A new type of phase transition is discussed which corresponds to a pairing of phonons of different lattice modes due to their
anharmonic attraction in a crystal. It is shown that the main features of the isostructural phase transition observed in SrTiO3 at T≃37 K can be explained qualitatively by the phonon pairing phenomenon.
Pis’ma Zh. éksp. Teor. Fiz. 67, No. 6, 399–404 (25 March 1998) 相似文献
10.
I. K. Polushina Yu. V. Rud’ T. N. Ushakova V. Yu. Rud’ 《Physics of the Solid State》1999,41(7):1084-1087
The first results obtained in studies of the temperature dependences of electrical conductivity and Hall constant of n-CdGeAs2 single crystals prepared by low-temperature crystallization are reported. It has been established that the method developed
permits growing single crystals with a free-electron concentration ⋍(1−2)×1018 cm−3 and a Hall mobility ⋍10000 cm2/(Vs) at T=300 K. It is shown that the temperature dependence of Hall mobility exhibits a behavior characteristic of electron scattering
by lattice vibrations, whereas below 150 K a deviation from this law is observed to occur evidencing an increasing contribution
of static lattice defects to scattering. The Hall mobility in the crystals prepared was found to reach ⋍36000 cm2/(Vs) at 77 K. Photosensitive heterojunctions based on n-CdGeAs2 single crystals were prepared. The spectral response of the photosensitivity of these structures is analyzed. It is concluded
that this method is promising for preparation of perfect CdGeAs2 crystals.
Fiz. Tverd. Tela (St. Petersburg) 41, 1190–1193 (July 1999) 相似文献
11.
This paper discusses how temperature/pressure processing affects the cascade of magnetic phase transitions in the alloy Fe0.5Mn1.1As with a C38 tetragonal crystal lattice. It shows that after various temperature/pressure treatment regimes (quenching of the sample
from 800 °C under pressures of 30–60 kbar) no transition to the low-temperature phase is observed, as a result of which the
ferrimagnetic phase extends to liquid-nitrogen temperatures. These results are analyzed on the basis of a qualitative model
that takes into account the competition of ferromagnetic and antiferromagnetic interactions within and between nonequivalent
crystallographic subsystems.
Fiz. Tverd. Tela (St. Petersburg) 39, 889–893 (May 1997) 相似文献
12.
We have performed extensive small-angle neutron scattering (SANS) diffraction studies of the vortex lattice in single crystal
YNi2B2C for B‖c. High-resolution SANS, combined with a field-oscillation vortex lattice preparation technique, allows us to separate Bragg
scattered intensities from two orthogonal domains and accurately determine the unit cell angle, β. The data suggest that upon increasing field there is a finite transition width where both low- and high-field distorted
hexagonal vortex lattice phases, mutually rotated by 45°, coexist. The smooth variation of diffracted intensity from each
phase through the transition corresponds to a redistribution of populations between the two types of domains. 相似文献
13.
An abundant set of published experimental NMR/NQR data on electric field gradients in ReBa2Cu3O7−δ
high temperature conductors, where Re=Y and Tm, is used as a test for the singlet-correlated band theory. Because of the
unusual spectral weight (“capacity”) of this band, it has been possible to match the number of holes per lattice site to photoemission
data on the energy spectrum and the location of the Fermi level. In the framework of a unified picture of the distribution
of holes (charges) it has been possible for the first time to explain satisfactorily the observed electric field gradients
at the Cu(1), Cu(2), O(1), O(2), O(3), and O(4) sites, as well as NMR and inelastic neutron scattering data on the crystal
electric field at the Tm ions.
Zh. éksp. Teor. Fiz. 111, 144–157 (January 1997) 相似文献
14.
A critical analysis of existing experimental and theoretical information on the lattice dynamics of the layered crystal α-HgI2 is performed. It is shown that a satisfactory understanding of the character of the interatomic interaction and characteristic
features of the phonon spectrum of this material can be obtained in a simple phenomenological model with eight parameters,
assuming that E
g/B1g
degeneracy of the 29 cm−1 Raman line is of a two-phonon nature.
Fiz. Tverd. Tela (St. Petersburg) 40, 537–541 (March 1998) 相似文献
15.
T. N. Antsygina V. A. Slyusarev K. A. Chishko 《Journal of Experimental and Theoretical Physics》1998,87(2):303-309
We solve the quantum mechanical problem of the inelastic scattering of phonons by a quadrupole defect in a crystal lattice
for the case of solid parahydrogen whose matrix contains pair complexes of H2 orthomolecules. By employing the pseudospin approximation for the operator of the energy of quadrupole-quadrupole interaction
of the molecules in an orthopair we derive an effective Hamiltonian that describes the interaction of phonons with a pair
quadrupole orthodefect in the lattice. We set up the scattering matrix and calculate the effective phonon relaxation time
τ(ω, T) as a function of the frequency ω and the crystal temperature T. We also find that a pair quadrupole defect, which has a complicated system of levels, can be replaced by an effective two-level
system with temperature-dependent parameters. The fact that a pair quadrupole orthocluster has internal degrees of freedom
results in a resonant scattering peak near a certain critical temperature T
0. Our estimates for H2 yield T
0≃ 6–7 K. Finally, we discuss the contribution of this mechanism to the low-temperature thermal conductivity of solid hydrogen.
Zh. éksp. Teor. Fiz. 114, 555–569 (August 1998) 相似文献
16.
The electronic energy structure of the defect system of c-BNx with ZnS-type structure is calculated in the multiple-scattering theory by the local coherent potential method. The cluster
version of the MT approximation is used to calculate the crystal potential. The effect of the relaxation of the crystal lattice on the electronic
structure of nonstoichiometric boron nitride c-BN0.75 is studied and a comparison is made with the electronic energy structure of c-BN in the same approximation.
Fiz. Tverd. Tela (St. Petersburg) 39, 1064–1065 (June 1997) 相似文献
17.
V. M. Gundyrev V. I. Zel’dovich 《Bulletin of the Russian Academy of Sciences: Physics》2010,74(11):1501-1508
A precision method for determining orientation relationships upon the B2 → B19′ transformation in titanium nickelide has been developed. The method is based on analyzing the martensite texture formed
in the initial high-temperature B2 phase of a single crystal having a high degree of perfection. The orientation relationships between the B19′ lattice and the initial B2 lattice of the TiNi single crystal were established from the B19′ martensite texture formed in single crystals of titanium nickelide upon the B2 → B19′ transformation and from measurements of the lattice parameters. Crystal mechanism of B19′ martensite was proposed which included the shear in the (21-1) B2 plane in the direction [−11-1] B2 by 10°. Such a shear system is typical of the bcc crystals at deformation by twinning. Absolute shear values are in a ratio
of 1:4 for B2 → B19′ transformation and for twinning, respectively. Martensite deformation at an invariant lattice is accompanied by small
rotations of martensite crystals (±1.6°), that increases the quantity of martensite orientations from 12 to 24. 相似文献
18.
L. P. Avakyants V. S. Gorelik É. M. Temper S. M. Shcherbina 《Physics of the Solid State》1999,41(8):1369-1372
Structure in the Raman scattering spectra of near-surface n-GaAs layers (n=2×1018 cm−3) implanted with 100 keV B+ ions in the dose range 3.1×1011–1.2×1014 cm−2 is investigated. The qualitative and quantitative data on the carrier density and mobility and on the degree of amorphization
of the crystal lattice and the parameters of the nanocrystalline phase as a result of ion implantation are obtained using
a method proposed for analyzing room-temperature Raman spectra.
Fiz. Tverd. Tela (St. Petersburg) 41, 1495–1498 (August 1999) 相似文献
19.
S. S. Aplesnin 《Physics of the Solid State》1997,39(5):800-802
A quantum Monte Carlo procedure is used to calculate the energy, sublattice magnetization, Néel temperature, and the slopes
of the S=[1/T
N(x=0)]dT
N(x)/dx curves as functions of the hole concentration and the exchange anisotropy Δ=1−J
x,y/J
z in the Heisenberg model with anisotropic negative interactions between nearest neighbors in a square lattice with dilution
among the lattice sites. The slope diverges in the limit Δ→0: S∼ln(6.5/Δ).
Fiz. Tverd. Tela (St. Petersburg) 39, 898–900 (May 1997) 相似文献
20.
Yu. F. Migal’ A. A. Lavrent’ev B. V. Gabrel’yan I. Ya. Nikiforov 《Physics of the Solid State》1998,40(12):1965-1968
The method of determining the structure parameters of multiatomic systems, using the spectra of soft x rays (XANES) proposed
earlier, is extended to the case of nonmetallic crystal bodies. This method is used to determine the lattice parameter and
the empirical muffin-tin potential from the positions of maxima of single-electron origin in the sulfur K spectrum in the compound CdS.
Fiz. Tverd. Tela (St. Petersburg) 40, 2168–2171 (December 1998) 相似文献